You know, there's only one place where I've come to think that self-chaining of mutators is a good idea, and that's in things like java's StringBuffer.append: basically, when the manipulator method is an accumulator of some sort.

So I've seen self-chaining, for example, in a C++ class that did checksums:

Here "dec" and "hex" aren't manipulators in the same sense as above, quite, but the syntax is clearly very similar. Again, though, the sense is that << is acting as an accumulator, and what passes through it adds on to what was there before, instead of being a "setter" method.

So getting back to Perl, this is in my opinion a perfectly respectable interface for a file-parsing library:

When putting a smiley right before a closing parenthesis, do you:

Use two parentheses: (Like this: :) )
Use one parenthesis: (Like this: :)
Reverse direction of the smiley: (Like this: (: )
Use angle/square brackets instead of parentheses
Use C-style commenting to set the smiley off from the closing parenthesis
Make the smiley a dunce: (:>
I disapprove of emoticons
Other